We've all been lectured about staying hydrated on hot summer days, but did you know that in the winter you can be a victim of cold weather dehydration?
Cold Weather Dehydration
Many schools and programs teach the importance of hydration as a factor of survival. All too often, however, this instruction revolves around, or is associated with, hot environments. In addition, many books place a great emphasis on staying well hydrated but put little detail in what that means, other than quantities such as “minimum of two liters a day”.
Unfortunately, this “generalized” information can lead the survivor into dangerous territory. Hydration is a very young and under-studied science, and got its beginnings with an individual named Pablo Valencia. Pablo, through a series of unfortunate events, found himself stranded in the Sonora desert of the United States for six days. When he finally reached civilization he was nursed back to health by WJ McGee, who later wrote the first case study on dehydration, “Desert Thirst as Disease”
Pablo’s incident and the subsequent study by McGee all occurred in the very early 1900’s. But it wasn’t until physiologists, mobilizing from the Harvard Fatigue Laboratory in World War II and conducting research at the Fort Knox Armored Medical Research Laboratory, that a true understanding of the effects of dehydration began to be understood. To this day, the primary research on dehydration comes from the US Army and their civilian contractors.
For the isolated person, dehydration from a hot environment may not be the most dangerous situation. This isn’t to downplay the dangers of a hot and arid environment, but rather to emphasize the dangers of a cold one. There are many reasons for emphasizing the danger of a cold environment, but the primary reason is lack of understanding.
As shown by modern studies, “the effect of air temperatures on thirst and drinking behavior consistently report depressed voluntary drinking during cold weather activities.” To a survivor this means that maintaining hydration is a willful act, and one which may not be regulated by the normal indicators of “thirst” (Water Requirements and Soldier Hydration; Scott J. Montain, PhD, and Matthew Ely, MS)
Also, there is a physiological reaction to cold which is called “cold-induced diuresis”, also known as an osmotic diuresis, and can increase urine water losses. (Water Requirements and Soldier Hydration; Scott J. Montain, PhD, and Matthew Ely, MS) This increased urine flow not only is involuntary, but it can rapidly lead to dehydration. This can be a dangerous situation since the body will continue this process until all the excess liquid is out of the body. In fact, when the desire to urinate stops, this is a flagrant warning sign that dehydration is just around the corner.
A third factor in cold dehydration is the air itself. Because cold environments tend to be “dry” the moisture is continually being “sucked” out of your body and as a result, according to research “cold environments increase the water vapor pressure gradient between the lungs and the atmosphere, more water is lost through respiration in cold environments than in warm environments.” (Water Requirements and Soldier Hydration; Scott J. Montain, PhD, and Matthew Ely, MS)
Finally, a person’s attempt at “survive” in a cold environment can lead to increase water loss. The heavy clothing worn not only restricts mobility but also leads to overheating. In addition moving through heavy been snow and exerting energy to create shelters, build fires and set signals can lead to increase loss of water. Statistics show “The addition of bulky clothing reduces mechanical efficiency and can increase the energy cost of a specific activity an additional 10% to 20%.99,100 The metabolic cost of movement in soft snow can be 2.5 to 4.1 times greater than performing the same activity on a blacktop surface.” (Water Requirements and Soldier Hydration; Scott J. Montain, PhD, and Matthew Ely, MS)
So as a survivor in a cold environment how do we adjust our techniques to stay hydrated? First, realize that “thirst” is not an indicator of needing to drink. As soon as possible, water should be ingested in continual small quantities (sips) to prevent dehydration from starting.
Next, cover your mouth with a rag! This is an old Yukon trick but does a couple of things to protect the survivor. First, it creates a barrier so cold air is not brought directly into the lungs lowering the body core temperature. Second is traps the outgoing respiration and reduces the moisture lost to the atmosphere. In extreme emergencies this frozen moisture can be recycled once warmed (i.e. after a fire is built) by sucking on the rag.
Third, is known as the COLDER principle and the “L” in COLDER stands for Loose/Layer. Surviving in a cold environment requires the constant adjusting of layers. Getting internal layers by over exertion is totally UNACCEPTABLE and can mean the difference between life and death. One, the wet clothes draw off body heat and can lead to hypothermia but also as the study shows water is being loss at increased levels. Not abiding by the loose/layer principle is setting yourself up for a double whammy!
The final point concerns the intake of fluids. When at all possible drink them warm or even hot. Warm fluids have numerous advantages over cold. One, your body isn’t forced to burn calories in order to warm them up prior to absorbing. Second, according to the same studies, they are more palatable and finally they have a positive psychological aspect. Of course a fire is the simplest way to warm liquids but carrying the water bottle between layers of clothing can also work.
The possibility of dehydration in a cold environment is a very real and dangerous threat. Understanding the dangerous and how to combat them is one step towards being a successful survivor.
USAF SERE (RET)
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